PIC18F1220ESLASHSOSQTP datasheet(190/308 Pages) MICROCHIP

190 / 308 page

PIC18F1220/1320

DS39605F-page 188

19.5.2

DATA EEPROM

CODE PROTECTION

The entire data EEPROM is protected from external

reads and writes by two bits: CPD and WRTD. CPD

inhibits external reads and writes of data EEPROM.

WRTD inhibits external writes to data EEPROM. The

CPU can continue to read and write data EEPROM,

regardless of the protection bit settings.

19.5.3

CONFIGURATION REGISTER

PROTECTION

The configuration registers can be write-protected. The

WRTC bit controls protection of the configuration

registers. In normal execution mode, the WRTC bit is

readable only. WRTC can only be written via ICSP or

an external programmer.

19.6

ID Locations

Eight

memory

locations

(200000h-200007h)

are

designated as ID locations, where the user can store

checksum or other code identification numbers. These

locations are both readable and writable during normal

execution through the TBLRD and TBLWT instructions,

or during program/verify. The ID locations can be read

when the device is code-protected.

19.7

In-Circuit Serial Programming

PIC18F1220/1320 microcontrollers can be serially

programmed while in the end application circuit. This is

simply done with two lines for clock and data and three

other lines for power, ground and the programming

voltage. This allows customers to manufacture boards

with unprogrammed devices and then program the

microcontroller just before shipping the product. This

also allows the most recent firmware or a custom

firmware to be programmed (see Table 19-4).

19.8

In-Circuit Debugger

When the DEBUG bit in configuration register,

CONFIG4L, is programmed to a ‘0’, the In-Circuit

Debugger functionality is enabled. This function allows

simple debugging functions when used with MPLAB®

IDE. When the microcontroller has this feature

enabled, some resources are not available for general

use. Table 19-5 shows which resources are required by

the background debugger.

TABLE 19-5:

DEBUGGER RESOURCES

To use the In-Circuit Debugger function of the

microcontroller, the design must implement In-Circuit

Serial Programming connections to MCLR/VPP, VDD,

VSS, RB7 and RB6. This will interface to the In-Circuit

Debugger module available from Microchip, or one of the

third party development tool companies (see the note fol-

lowing Section 19.7 “In-Circuit Serial Programming”

for more information).

Note:

The Timer1 oscillator shares the T1OSI

and T1OSO pins with the PGD and PGC

pins

used

for

programming

and

debugging.

When using the Timer1 oscillator, In-Circuit

Serial

Programming

(ICSP)

may

not

function correctly (high voltage or low

voltage), or the In-Circuit Debugger (ICD)

may not communicate with the controller.

As a result of using either ICSP or ICD, the

Timer1 crystal may be damaged.

If ICSP or ICD operations are required, the

crystal should be disconnected from the

circuit (disconnect either lead), or installed

after programming. The oscillator loading

capacitors may remain in-circuit during

ICSP or ICD operation.

TABLE 19-4:

ICSP/ICD CONNECTIONS

Signal

Notes

PGD

RB7/PGD/T1OSI/

P1D/KBI3

Shared with T1OSC – protect

crystal

PGC

RB6/PGC/T1OSO/

T13CKI/P1C/KBI2

Shared with T1OSC – protect

crystal

MCLR

MCLR/VPP/RA5

VDD

VSS

PGM

RB5/PGM/KBI1

Optional – pull RB5 low is

LVP enabled

I/O pins:

RB6, RB7

Stack:

2 levels

Program Memory:

512 bytes

Data Memory:

10 bytes

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